Diesel oil removal from water by froth flotation under low interfacial tension and colloidal gas aphron conditions

The objective of this work was to investigate the relationship between the froth characteristics, the system interfacial tension (IFT), and the efficiency of diesel oil removal by froth flotation under colloidal gas aphron (CGA) conditions. Branched alcohol propoxylate sulfate sodium salt (C14–15(PO)5SO4Na) as an extended surfactant, was used to form CGA and microemulsions with diesel oil. For the CGA studies, the effects of salinity, surfactant concentration, stirring speed, and stirring time were investigated in order to determine the optimum conditions of the CGA formation which were further used for the froth flotation experiments. The air bubble size measurement was carried out in order to correlate the air bubble size to the froth flotation performance. The results showed that the use of CGA enhanced the process performance of froth flotation in terms of both the removal and the enrichment ratio of diesel oil since CGA increased both froth formation and stability. The froth flotation column which was operated at an air flow rate of 0.30 l/min with the feed solution prepared under non-equilibrium and the CGA conditions at 0.1 wt.% C14–15(PO)5SO4Na, 3 wt.% NaCl, with a stirring speed of 5000 rpm and a stirring time of 5 min, gave the highest oil removal of 97%.